25 research outputs found
Retrieval of dispersive and convective transport phenomena in fluids using stationary and nonstationary time domain analysis
Simultaneously occuring dispersive and convective components of fluid kinematics are obtained by a time domain analysis of optically retrieved temporal histories of the transport phenomena. Utilizing triangulation of collimated optical fields of view from two radiometers to obtain the temporal histories of the intensity fluctuations associated with the transport phenomena has enabled investigators to retrieve the local convective transport by employing correlation statistics. The location of the peak in the covariance curve determines the transit time from which the convection velocity is calculated; whereas, the change in shape of the peak in the covariance curve determines the change in average frequency of the wave packet from which the dispersion velocity is calculated. Thus, two-component analysis requires the maximum possible enhancement of the delineation for the transport. The convection velocity is the result of a fixed reference frame calculation whereas, the dispersion velocity is the result of a moving reference frame calcuation
Recruitment of Baltic cod and sprat stocks: identification of critical life stages and incorporation of enviromental variability into stock-recruitment relationships
The recruitment processes of Baltic cod and sprat were analysed and critical periods were identified by addressing the major impact factors on individual early life history stages separately and relating observed abundance data between successive stages. For cod, recruitment appeared to be dependent on egg survival, with low oxygen concentration in dwelling depths and predation by clupeids as the major causes for egg mortality. Surviving egg production and larval abundance were weakly correlated, whereas larval abundance was significantly related to year class strength. This indicated that the period between the late egg and the early larval stage is critical for cod recruitment. A potential variable identified to affect this life stage was prey availability for larvae. For sprat, early and late egg stage production as well as late egg stage production and larval abundance were significantly related. However, year class strength was largely independent of larval abundance. Thus, the period between the late larval and early juvenile stage appeared to be critical for sprat recruitment. Potential variables identified to affect this life stage were ambient temperature and wind stress. Environmental factors showing statistically significant covariance with the survival of one of these critical life stages were incorporated into stock-recruitment models for individual spawning areas separately and for the Central Baltic combined
Short-term temporal variation in PM2.5 mass and chemical composition during the Atlanta Supersite Expriment, 1999
Measurements in urban Atlanta of transient aerosol events in which PM2.5 mass concentrations rapidly rise and fall over a period of 3-6 hr are reported. The data are based on new measurement techniques demonstrated at the U.S. Environmental Protection Agency (EPA) Atlanta Supersite Experiment in August 1999. These independent instruments for aerosol chemical speciation of NO3-, SO4(2-), NH4+, and organic and elemental carbon (OC and EC), reconstructed the observed hourly dry PM2.5 mass to within 20% or better. Data from the experiment indicated that transient PM2.5 events were ubiquitous in Atlanta and were typically characterized by a sudden increase of EC (soot) and OC in the early morning or SO4(2-) in the late afternoon. The frequent temporal decoupling of these events provides insights into their origins, suggesting mobile sources in metro Atlanta as the main contributor to early morning PM2.5 and more regionally located point SO2 sources for afternoon PM2.5 events. The transient events may also have health implications. New data suggest that short-term PM2.5 exposures may lead to adverse health effects. Standard integrated filter-based techniques used in PM2.5 compliance monitoring networks and in most past PM2.5 epidemiologic studies collect samples over 24-hr periods and thus are unable to capture these transient events. Moreover, health-effects studies that focus on daily PM2.5 mass alone cannot evaluate the health implications of the unique and variable chemical properties of these episodes
Event generator tunes obtained from underlying event and multiparton scattering measurements
New sets of parameters (âtunesâ) for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE protonâproton (pp) data at âs =7TeV and to UE protonâantiproton (pp ÂŻ) data from the CDF experiment at lower âs, are used to study the UE models and constrain their parameters, providing thereby improved predictions for protonâproton collisions at 13TeV. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to âminimum biasâ (MB) events, multijet, and DrellâYan (qq ÂŻ âZ/Îł â â lepton-antilepton+jets) observables at 7 and 8TeV, as well as predictions for MB and UE observables at 13TeV.
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Status of Advanced Tokamak Scenario Modeling with Off-Axis Electron Cyclotron Current Drive in DIII-D
The status of modeling work focused on developing the advanced tokamak scenarios in DIII-D is discussed. The objectives of the work are two-fold: (1) to develop AT scenarios with ECCD using time-dependent transport simulations, coupled with heating and current drive models, consistent with MHD equilibrium and stability; and (2) to use time-dependent simulations to help plan experiments and to understand the key physics involved. Time-dependent simulations based on transport coefficients derived from experimentally achieved target discharges are used to perform AT scenario modeling. The modeling indicates off-axis ECCD with approximately 3 MW absorbed power can maintain high-performance discharges with q{sub min} > 1 for 5 to 10 s. The resultant equilibria are calculated to be stable to n = 1 pressure driven modes. The plasma is well into the second stability regime for high-n ballooning modes over a large part of the plasma volume. The role of continuous localized ECCD is studied for stabilizing m/n = 2/1 tearing modes. The progress towards validating current drive and transport models, consistent with experimental results, and developing self-consistent, integrated high performance AT scenarios is discussed
The Organizationally Dependent Community: A Comparative Study of Neighborhood Attachment
We introduce the concept "organizationally dependent" community to describe communities that lack the basis for developing attachment through informal social integration and in which the primary source of attachment is participation in formal organizations created to protect the community from outside threats. Neighborhoods experiencing residential renovation are examples of organizationally dependent communities. Because renovators are newcomers to their neighborhoods they cannot rely on informal social networks to solve neighborhood problems, but they can become involved in formal organizations to do so. This type of participation becomes an important source of neighborhood attachment. Data testing this hypothesis, generally, are consistent with it.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline